Method and apparatus for grinding gears



July 21 1931. B. E. SHLESINGER ET AL 1,315,336

METHOD AND APPARATUS FOR GRINDING GEARS Filed Feb. '28. 1929 s Sheets-Sheet 1 "Ml 111W INVENTOR irmwares? BY -Dvgxmv ATTORNE July 21, 1931. B. E. SHLESINGER ET AL METHOD AND APPARATUS FOR GRINDING GEARS Filed Feb. 28, 1929 3 Sheets-Sheet 2 lNV NTOR,

EJIILESINGIR 8r I'M Dwuaw A'ITORNEY4 July 21, 1931. B. 5. SHLESINGER ET AL 1,315,336

METHOD AND APPARATUS FOR GRINDING GEARS Filed Feb. 28, 1929 3 Sheets-Sheet 5 INVENTOR B E Snwsmam 8f TN. DVRKAN Q9 BY ATTORNEY @atted juiy 2i, 1%33 Nara stares PATENT OFFICE] BERNARD E. OF IRONDEQUOIT, AND THOMASM. DUBKAN, OF ROCHESTER,

NEW YORK, ASSIGNORS '10 GLEASON WORKS, OF ROCHESTER, NEW YORK, A COB- IPORATION OF NEW YORK ammo AND arrann'rus FOR GRINDING snans Application filed February 28, 1929. Serial No. 343,329.

The present invention relates to a method.

and to apparatus for finishing longitudinally curved tooth gears by grinding.

The primary ob'ect of this invention is to provide a met 0d and apparatus for grinding longitudinally curved tooth gears which will produce gears of extreme accuracy.

A further object of this invention is to provide a method and apparatus for grinding longitudinally curved tooth gears which will increase the rate of production over previous grinding methods and effect a material reduction in the time required to grind a lon itudinally curved tooth gear.

A urther object of this invention is to.

grind longitudinally curved tooth gears in a continuous indexing process.

Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims.

In the drawings:

Figure 1 shows a grinding wheel of the dished type, such as is preferably employed with this invention, in grinding engagement with a longitudinally curved tooth bevel or hypoid gear and illustrates diagrammatically the principles on which the present invention operates;

Figure 2 is a sectional view of the grinding wheel and gear taken in a plane tangent to the pitch surface of the gear or in any plane parallel thereto and illustrating further the principles on which this invention is based;

Figure 3 is a sectional view of the grindilig wheel and gear in grinding engagement taken in a plane passing through the axis of the wheel;

Figure 4 IS a plan view showing diagram-v matically how a plurality of grinding wheels may be employed to produce gears by the process of this invention and'increase the eifective grinding time over that of a single grinding wheel; v

Figure 5 is a section on the line 5-5 of Figure 4; igure 6 is a section takenin the pitch plane of the gear .bei'n ground or in any plane parallel thereto s owing'the relative positions of the gear [and the of a machine embodying a practical application 0f this invention; and

Figure 8 .is a section on the line 8-8 of Figure 7.

\Vith the present invention, longitudinally curved tooth gears are ground in a continuous indexing process. In this process, a grinding member and the gear to be ground are rotated continuously together in such timed relation that the grinding member enters a different tooth space of the gear on each successive passage of the grinding member across the face of the gear. The tooth faces of the gear are thus ground simultaneously and finished substantially simultaneously. This process results in gears having very accurate tooth spacing because any wear of the Wheel is distributed over all the teeth and undue heating of the gears at any one point, which may cause distortion, is avoided. The continuous rotation of the gear in this process serves, moreover, to automatically index the gear in the period between the successive operations of the grinding member or members The complicated and expensive indexing mechanism which has heretofore been required is, therefore, no longer necessary.

A further prime advantage of the new process is the speeding up of the whole .until the high spot is reached. In this way; idle, non-working feeding time, a characteristic of previous grinding methods is eliminated.

the preferred embodiment of this invention, a dished grinding wheel is employ ed as the grinding element. With such a wheel it is possible to obtain a suflicient and a uniform clearance between the grinding surface of the wheel and of the gear tooth surface being ground as the wheel passes across said surface so that burning of the tooth surface is entirely avoided. In operation, the wheel is rotated on its own axis and simultaneously revolved about another axis the location of which is determined by the spiral angle desired for the gear teeth. The revolution of the wheel about this last named axis is timed with the rotation of the gear as already indicated. The curve ground on the gear will be a resultant of the bodily movement of the grinding wheel and of the rotation of the gear on its own axis and will be a form of cycloid and not a true circular are. This curve can be made to approach, however, closely to. a circular arc and to produce only such slight modification of the lengthwise tooth curve of the gear tooth as will roduce a desirable localization of the bearing of a pair of gears in mesh and give the gears just enough adjustability to allow them to accommodate themselves to different conditions of mounting and to the variations of load which occur in use. Hence, on the one hand the method of the present invention can be employed to grind gears which have been pre viously cut with a rotary'annu'lar facemill and on the other hand gears ground according to this invention will interchange with gears cut with a face mill.

To reduce the amount of idle time, it has been found desirable in practise to use more than one grinding'wheel, the several wheels operating successively on separate tooth faces of the gear. In the construction of a machine for practising the invention, the employment of a plurality of wheels has been found an advantage in another way in e that it makes for a more balanced condition. So when, for instance, three'wheels are used, the wheels will balance each other completely during the rotation of the head on which they are mounted, thereby eliminating any tendency to an unbalanced con- .dltion which might set up vibrations.

Referring to the drawings by numerals of reference, Figures 1 and 2 illustrate the invention in a general aspect. 10 indicates the gear to be ground, a bevel or hypoid gear provided with longitudinally curved teeth 11. 12 designates the grinding wheel WlllCh is shown in the act of grinding on one of the tooth surfaces of the gear 10. The grinding wheel 12. as clearly shown in Figures 1 and 3, is of the dished type. The inside and outside surfaces 13 and 14, respectively, of the wheel constitute its active grinding surfaces. Gears to be ground are ordinarily previously cut slightly greater than full depth so that the tip surface 15 of the grinding wheel does no work.

In the wheel 12 shown, the inside surface 13 and the outside surface 14.- are truncated conical surfaces whose apexes lie both on the same side of a plane perpendicular to the axis 16 of the wheel at its tip. In axial section, the wheel has an active grinding surface in the form of a rack tooth, both sides of which are straight as shown clearly in Figure 3. The purpose of this construction will appear hereinafter.

The axis 16 of the grinding wheel is inclined at an acute angle to a plane such as indicated at 19 in Figure 1 tangent to the pitch surface of the gear 10. In the tangent plane 19 the grinding wheel is of general crescent shape as clearly shown in' Figure 2. The crescent shape of the dished wheel is a marked advantage for by' reason of this shape suflicient clearance to prevent burning of the tooth surfaces is provided between the side surfaces of the wheel and the side surfaces of the gear tooth or teeth being ground, as the wheel passes across the tooth surface or surfaces.

In ractise, the spiral an le to be produced on t e gear tooth is first determined. Knowing the ratio of rotation of the gear to the bodily rotation of the wheel, the location of the axis 18 about which the wheel is bodily rotated can, then, be readily determined, for the Wheel is positioned, preferably,'so that its axis 16 projected into the tangent plane 19 is normal to the tooth side to be ground atthe center of the gear face and. the axis 18 is offset from the axis 19 by the amount necessary to maintain the clearance inherent in the crescent shape of the Wheel as the wheel moves across the face of the continuously rotating gear. The position of the axis 18 is determined then, by subtracting from the desired to'oth spiral angle, the angle required between the axis 18 and the axis 16 to secure a satisfactory wheel clearance. As clearly shown in Fig. 2,-then, the wheel is positioned so that its axis 16 is normal to the tooth surface bein ground at the center of the tooth face and the axis 18 is so offset from the axis 16 by the amount necessary to incline the crescent shaped active section of the wheel to the circular path 20, on which the wheel travels about the axis 18, that a substantially uniform clearance is maintained between the wheel and tooth surface of the gear as the wheel moves across the face of the continuously. rotating gear.

In operation, the grinding wheel is continuously rotated on its axis 16 and simultaneously rotated about the axis 18 and the gear 10 is rotated continuously on its own axis in intermeshing engagement with the wheel. This rotation of the gear on its axis is so timed relative to the bodily movement whereby the grinding wheel operates on a differenttooth surface of the gear in each wheel.

passage across its face.

With a single wheel it will be seen that, the wheel has to travel all around the circle 20 after making one passage across the face of a gear before making the second passage across a new tooth surface. To reduce the amount of idle time in the grinding operation, it has been proposed to employ a plurality of grinding wheels properly spacedabout the axis 18 and all traveling'on thecircle 20. Such an arrangement is shown diagrammatically in Figures 4, 5 and 6.

Here three grinding wheels 12, 12" and 12" are employed. These wheels are of the same shape as the wheel 12 already described. They are positioned so that their axes 1G. 16 and 16 are inclined to the pitch plane 19 of the gear 10 by the amount required to positionthe wheels so that. the active rack-tooth shaped-axial section of the grindingwheels will be in proper relation with the gear 10 to be ground. The axes 16, 16 and 16 are positioned, also, in such offset relation to the axis 18 about which the wheels revolve that the proper clearance will be maintained between the side surfaces of the wheels and, the side surfaces of the gear teeth .being ground as the wheels pass successively across the face of the gear. So, again, the uniform clearance inherent in the crescent shaped tangent plane section of the grinding wheels is maintained despite the continuous rotation of the gear.

lVith the three grinding wheels 12, 12 and 12", each is rotated on its own axis 16, 16 and 16", as the case may be, and all are simultaneously revolved about the axis 18. Due to the continuous rotation of the gear 10 on its axis, the grinding wheels enter successively different tooth faces of the gearf The conical grinding wheels of Figures 1 to 6 inclusive are employed because of the rack-toothed axial section which is peculiar to thestructure of a dished shape conical By the usewof such a wheel with its rack-toothed section, a basic rack for spur gears or a basic crown gear for bevel and hypoid gears may be represented by the grinding wheel and gears generated conjugate to the basic rack or crown gear, as the case may be. The generating motion employed will be the usual generating motion employed in cutting spur gears or bevel or hypoid gears conjugate to a basic rack or crowngear, as the case may be, namely, a relative rolling motion between the grinding wheel and gear being ground as though the gear were rolling on the basic rack or on the basic crown gear. The rolling motion may be applied all to the wheel orall to the gear or dividedbetween the wheel and gear, as in the usual method of generating gears in a cutting operation. In the case of bevel and hypoid gears, moreover, the basic crown gear may be a true crown gearor a nominal crown gear as in the usual practice.

Figure 6 illustrates diagrammatically the operation of grinding a gear 10 with three grinding wheels, 12, 12 and 12" in a generating operation according to this invention. .This view is a sectional view taken in. a plane tangent to the pitch surface of the gear 10 or in anyplane parallel thereto. The wheels are positioned with their axes inclined to tlie'tangent plane and offset from the axis 18 about which they are revolved as previously described. In the drawings, the generating motion is shown as divided between the gear and the wheels. In other words, in a generating machine, the wheels would be, mounted upon a cradle or face plate which is given a slow generating motion and the gear would have, in addition to its continuous indexing rotation an added slow generating rotation in the proper ratio with the cradle movement to produce a rolling motion between the wheel and gear, as though the gear were rolling on a basic crown. gear represented by the wheels. In this generating motion, the axis 18 about which the wheels revolve moves slowly about the axis 22 representing the axis of the crown gear. Because ofthis slow generating motion, the axis 18 assumes successive positions 18, 18a and 18b and the path of wheel travel moves successively from the position 20 to the position 200 and thence to the position 20?) etc. Because of the continuous indexing rotation of the gear and the timed relation between this rotation and the movement of the wheels 12, 12' and 12" about the .axis 18, the wheels enter successively successive tooth spaces of the gear to grind successive tooth surfaces thereof. Thus, as shown, the wheel 12 enters the tooth space 23 grinding one or both side surfaces of this tooth space, as may be de-' sired, as the gear revolves under the wheel and as the wheel passes across the face of the gear. The continuous rotation of the gear and revolution of the wheels about the axis 18 then causes the'wheel 12 to enter the next tooth space 24 and the wheel 12" to enter the succeeding tooth space 25. further rotation of the gear and revolution of the wheels about the axis 18, the wheel 12 will enter the space 26 and so each wheel enters a different tooth space from the preceding wheel or. the succeeding wheel in one revolution of the wheels about the axis 18.

The invention is not restricted to the grinding of gears in a generating operation,

In the provide proper grinding clearance.

tool head is adjustable in a mannersimilar ,in the frame or-base of the machine.

but may be employed also in grinding "gears in a forming or non-generating process.

In Figures 7 and 8 we have'illustrated somewhat diagrammatically one embodiment of a machine for practising this invention in the grin'din of bevel or hypoid gears. Here the grinding wheels 12, 12 and 12 are shown mounted upon spindles 25 which are 'journaled in any suitable manner in a rotatable tool head 26 which is rotatably mounted in the cradle or face plate 27. The axis of the cradle 27 corresponds to the axis of the crown gear represented by ,the grinding wheels and on which the gear rolls theoretically in the generating process. Theaxis of the grinding wheels are inclined to a plane tangent to the pitch surface of the gear 30 to be ground as shown clearly m- Figure 8 and are offset from the axis 31 of the tool head 26 by the amount necessary Ito T e to face mill cutters on cutting machines to permit grinding gears of different spiral angles.

The gear 30 to be gi dund is secured to a work spindle 32 which is journaled in suitable bearings, one of which is .shown atT33,

he gear 30 is rotated continuously on its axis by means of a worm wheel 34 to which power is continuously applied during the operation of the machine.

The cradle 27 is also rotated continuously on its axis by means of a worm 35. which meshes with a worm wheel secured to the cradle 27 and which is driven continuously during the operation of the machine. The grinding wheels are driven continuously from a shaft, 36 to which power may be applied in any suit able manner by means of a spur gear 37 which meshes with three spur pinions 38, one corresponding to each of the grinding wheels. These'spur pinions 38 are mounte upon shafts 39 to which are secured bevel gears 40'. The bevel gears 40 mesh, respectively with bevel gears 41 which are secured, respectively, to the several spindles 25 on which the grinding wheels are mounted. The tool head is rotated contin'uously about its axis 31 by means of a spur pinion 43 which is secured to the shaft 36 and which drives through a.spur gear 44 an .internal gear 45 which is secured to the tool head. r

It will be seen, therefore, that by the means described, the grinding wheels are rotated continuously on their axes and continuously revolved about the axis 31 of the serves to feed the grinding wheels into full employed in bobbing machines to maintain .the timed relation between the tool and the work.

The means for obtaining the required mo tions in a spiral bevel or hypoid grinding generator has been described. The interconnecting gearing-may take any suitable form and it has not been deemed necessary to illustrate it here. Reference may be had, for instance, to the-patent to James E. Gleason et al. Reissue No. 15,759 of February 12, 1924, which illustrates one way in which the work, tool head and cradle may be interconnected.

tax

While the invention has been described in connection with the use of a particular type of grinding wheel it is to be understood that the invention is not to be construed as limited to practice with such a form of wheel. In general, it may be said that while we have described one particular embodiment of our invention, it is to be understood that the invention is capable of further modifications and that this application is intended to cover any variations, uses, or

adaptations of the invention following, in

general, the principles of the invention andincluding such departures from the present disclosure a come within known or customary practise in the gear art and as may be applied to the essential features hereinbefore set forth and as fall within the scope 1 of the invention or the limitsof the append ed claims.

Having thus described our invention, what we claim is:

1. The method of grinding a longitudinally curved tooth gear which consists in rotating a grinding wheel on its axis while moving the wheel continuously in a closed path and imparting simultaneously to the gear a continuous rotary motion in such timed relation to the last named movement of the wheel that the gearis continuously indexed.

2.. The method of grinding a gear which consists in rotating a dished grinding wheel on its axis while moving the wheel continuously in a closed path and imparting simultaneously to the gear a continuous rotary motion in such timed relation with the last named movement of the wheel that the gear is continuously indexed.

3. The method of grinding a gear which l'oU consists in rotating a grinding wheel on its axis while moving the wheel continuously in a closed circular path and imparting simultaneously to the gear in timed relation with the last named movement of the wheel a continuous rotary motion. which combines with the continuous movement of the wheel in a closed path to produce the longitudinal tooth curve and to index the gear.

4. The method of grinding a longitudinally curved tooth gear which consists-in Tome ing a dished grinding wheel on its axis while moving the wheel continuously in a closed circular path and imparting simul-.

taneously to the gear a continuous rotary motion in timed relation with the last' moving the wheel 'conti uously in a closed path and in imparting simultaneously a con tinuous rotary motion to the gear in timed relation with the last named movement ofthe wheel and simultaneously producing a relative rolling motion between the wheel and gear to generate the tooth profiles.

6. The method of grinding a gear which consists in rotating a dished grinding wheel having active grinding surfaces which are portions of the'outside and inside surfaces of the wheel on its axis while moving the wheel continuously in a closed path and imparting simultaneously to the gear a continuous rotary motion in timed relation with the last named movement of the wheel.

7 The method of grinding a ear which consists in rotating a dished grin ing wheel, having conical grinding surfaces whose apexes lie on the same side of a plane perpendicular to the axis of the wheel at its tip, on its axis while moving the wheel continuously in a closed circular path and imparting simultaneously to the gear a continuous rotary motion in timed relation with the last named movement of the wheel.

8. The method of grindinga gear which consists in rotating continuously in a closed path a grinding member having an effective operating portion which is of general crescent shape in a plane tangent to the pitch surface of the gear and simultaneously imparting to the gear a'continuous rotary motion which. cooperates with the motion of the grinding member to eifect grinding of the longitudinal tooth surfaces of the gear and continuous indexing of the gear.

9. The method ofgrinding a gear which consists in employing a plurality of dished grinding wheels, rotating the rinding wheels on their respective axes whlle moving the wheels continuously in a closed path and simultaneously imparting to the gear a continuous rotary motion on 1ts axis in such timed relation with the last named movement of the wheels that the successive wheels enter successively difi'erent tooth spaces of the gear.

10. The method of grinding a gear which consists in rotating a plurality of grinding members, each having an effective operating portion of general crescent shape in a plane tangent to the pitch surface of the gear continuously in a closed circular path an simultaneously imparting a continuous rotary motion to the gear in timed relation with the movement-of said grinding members to grind the longitudinally curved tooth surfaces of the uous indexing thereo 11. The method of grinding a gear which consists in positioning a dished rotary grinding wheel so that its tip surface lies in a plane tangent to the root surface of the gear to be ground and its axis is inclined to said plane and offset from a second axis perpen dicular to said plane, and rotating the wheel on its axis while simultaneously moving it continuously in a closed path about the second axis and simultaneously imparting a continuous rotary motion to the gear on its axis to grind the longitudinally curved tooth surfaces of the gear and effect continuous indexin thereof.

12. T e method of grinding a longitudinally curved tooth gear which conslsts in positioning a plurality of grinding wheels so that their tip surfaces lie in' a plane tangent to the root surface of the gear to be ground and so that their respective axes are offset from a second axis perpendicular to said plane and rotating the wheels on their axes while simultaneously moving them bodily in a closed path about the second axis "and simultaneously rotating the gear continuously on its axis so that successive wheels enter successively different tooth spaces of the gear.

13. In a machine for grinding longitudinally curved tooth gears, the combination with a work support, of a-rotary grinding wheel, means for rotating the grinding wheel on its axis, means for moving the grinding wheel continuously in a closed gear and efiect continpath and means for imparting a continuous tinuous rotary motion to the work support in timed relation tothe last named movement of the grinding wheel.

15. In a machine for grinding longitudinally curved tooth gears, the combination .with a work support of a rotary dished grinding wheel, means for rotating the grinding wheel on its axis, means for moving the grinding wheel continuously in 10 closed circular path, means for imparting a continuous rotary motion to the work sup-v port in timed relation with the last named movement of the grinding wheel, and means for simultaneously producing a relative rolling motion between the wheel and gear.

16. In a machine for grinding longitudinally curved tooth gears, the combination with a work support of a rotary tool head, a plurality of rotary dished grinding wheels journaled in said head in spaced relation to each other with their axes offset from the axis of said head and inclined to a plane tangent to the pitch surface of the gear to be ground, means for rotating the wheels on their respective axes, means for rotating the head continuously on its axis and means for simultaneously imparting a continuous rotary movement to the work support so timed with the rotation of the head that the 3 successive grinding wheels enter successively difierent tooth faces of the gear during a sin le revolution of the tool head.

1 In a machine for grinding longitudinally curved tooth gears, the combination with a work support, of a rotary tool head, a plurality of rotary dished grinding wheels journaled in said head in spaced relation to each other with their axes ofiset from the axis of said head and inclined to a plane tangent to the pitch surface of the gear to be ground, means for rotating the wheels on their respective axes, means for rotating the head continuously on its axis, means for simultaneously imparting a continuous rotary movement to the work support so timed with the rotation of the head that the grinding wheels enter successively. difierent tooth spaces of a blank during a single revolution of the tool head, and means for simultaneously pjoducing a relative rolling motion between the wheel and work support, such rolling. motion acting in addition to generating profiles of vthe teeth of the gear to move the grinding Wheels so as to grind the tooth surfaces of the gear to full depth over their entire face.

B. E. SHLESINGER. T. M. DURKAN. 

